Electron tube



June 28, 1'966 M. scl-l'lEKEL ELECTRON TUBE Filed March 2, 1964 Fig] RTTURNYS United States Patent O 3,258,637 ELECTRON TUBE Manfred Schiekel, Ulm (Danube), Germany, assgnor to Telefunken Patentverwertungs-G.m.b.H., Ulm (Danube), Germany Filed Mar. 2, 1964, Ser. No. 348,639

Claims priority, application Germany, Mar. 8, 1963,

6 Claims. (Cl. 313-350) The present invention relates generally to a double frame grid for electrical discharge tubes.

It is common for an electrical discharge tube, for example, an electron tube, to have two grids mounted on a single mechanical structure. Such structure ordinarily consists of two nested pairs of rods of different diameter, which are held together by common cross pieces at their extremities.

In one known construction of a double frame grid, the inner pair of rods is made of metal, while the outer pair of rods is made of ceramic. The manufacture of such rods is as follows: first, each pair of rods is machined to the desired shape. 'Ilhen one of each pair of rods is soldered to one of the other pair, one of the surfaces of each ceramic rod having previously been metallized.

One drawback of this type of construction lies in the fact that the machining operation for the rods is eX- tremely expensive. Another drawback is that a high capacitance exists between the two grids which are wound onto the pairs of rods, because the electric field between the two grids, at each end of the structure, lies within one of the ceramic rods, which have relatively high dielectric constants. Since the two rods are in contact along their entire length, the inter-grid capacitance is relatively high.

A fur-ther drawback to the conventional structure is that the outer grid which is wound onto the ceramic grids, can carry only relatively small currents. The reason for this is the low thermal conductivity of the ceramic rods, and consequently their low rate of heat dissipation.

It is, therefore, an object of the present invention to provide a double frame grid for electric discharge tubes which overcomes the above-mentioned drawbacks.

A further object of the invention is to provide a double frame grid structure for electric discharge tubes which is simple and inexpensive to manufacture.

With the above objects in View, the present invention is based on a double frame grid which consists of two nested pairs of rods of dilerent diameter, of transverse cross pieces which hold the rods, and of two wire windings, one of which is wound upon each of the pairs of rods. According to the present invention the outer rods are of greater diameter than the inner rods. Rings of insulating material are placed on the outer rods at their ends, and the rods are inserted within cross pieces, which it about the insulating rings.

The outer rods can be soldered into the transverse or cross pieces, or they can be held within the enlarged ends of these cross pieces solely under the influence of friction. When the outer grid is wound onto the rod under tension, a pull is exerted which holds the outer rods in position in the cross pieces.

If the outer rods are to be soldered into the transverse pieces, the insulating rings are preferably made of ceramic. The peripheral surfaces of these ceramic rings are then metallized, to facilitate soldering.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is an elevational view of a frame grid according to the present invention.

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FIGURES 2 and 3 are sectional views of two embodiments of the present invention.

Referring now to the drawings, the rods 1 which hold the inner grid are preferably made of molybdenum, as are the rods 2 which hold the outer grid. The diameter of the rods 2 is larger than that of the rods 1. The relative diameters of the two sets of rods is determined by the desired spacing between the inner and outer grids. Transverse or cross pieces 4 (FIGURE 2) or 8 (FIG- URE 3) are arranged in sets of two, and soldered to the rods 1, one of each set being directly opposite the other of the set. The ends 5 and 9, respectively, of transverse pieces 4 and 8 are shaped so as to provide a wider separation between the cross pieces at their ends than at a point midway between the ends. Within the resulting widened ends are fit the rods 2. However, before the outer rods are soldered in place, ceramic insulating rings 3 are soldered onto their ends, at least a portion of the periphery of these rings having been metallized, The rods 2 are then soldered into the transverse pieces 4 in such a manner that the ceramic rings 3 come to lie between the widened ends of the transverse pieces.

The embodiment of FIGURE 2 differs from that of FIGURE 3 in that in FIGURE 2 the transverse pieces are simply flared at the ends, whereas the transverse pieces shown in FIGURE 3 are provided with shoulders. In the resulting structure, the two cross pieces of a set thereof have parallel central portions spaced a distance from one another equal to the diameter of the inner pair of rods, and parallel end portions, spaced from each other a distance equal to the diameter of the insulating rings. Under certain circumstances, the latter arrangement makes it possible to conform more closely to the specified tolerances.

The double frame grids are produced as follows: iirst, the rods 1 are `soldered to the transverse pieces 4. The grid winding 6 of the inner grid is then wound in place. The rods 2 are then soldered in place and the outer grid 7 wound onto them. The grid windings themselves are soldered to .the rods so that they may not slip.

It Iwill be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. A double `frame grid for electric discharge tubes, comprising, in combination:

a lirst pair of spaced, substantially parallel rods,

a second pair of spaced, substantially parallel rods of larger diameter than said iirst pair of rods, said first and second pairs of rods being parallel to each other with said first pair of rods being disposed between said second pair lof rods,

a plurality of cross pieces which hold the rods, said cross pieces being arranged in sets of two, the cross pieces of each set being disposed, respectively, on opposite sides of said rods, the distance between the cross pieces of each set being different in the reg-ion of said rst and second pair of rods, respectively,

a plurality of insulating rings on each of the second pair of rods, there being .a ring at each intersection of a cross piece with one of said second pair of rods, and

first and second grids wound, respectively, on said iirst and second pairs of rods.

- 2. A double frame grid as defined in claim 1 wherein the distance between said cross pie-ces increases gradually from said first pair of rods to said second pair of rods.

3. A double frame grid as defined in claim 1, wherein said cross pieces are arranged substantially parallel between the outer sides of the `first pair of rods, the distance between said cross pieces increasing abruptly ,to form `a shoulder to seat the second pair of rods, said cross pieces then continuing substantially parallel to one another.

4. A double frame grid as defined in claim 1 'wherein the cross pieces of each set include parallel central portions which are spaced from each other a distance equal to the diameter of said irst pair of rods, and parallel end portions which are spaced -from each other a distance equal to the diameter of said rings.

5. A double frame grid as defined in claim 1 'wherein 10 said rings are made of ceramic material.

6. A double frame grid as defined in claim :5 wherein the ceramic rings have metallized peripheral surfaces and Aare soldered into place between the cross piece-s.

References Cited by the Examiner UNITED STATES PATENTS Re. 15,278 1/1922 Langmuir 313-350 X 2,738,436 3/1956 Zaphiropoulos 313-348 X 2,960,621 11/1960 Lane et al 313-350 3,168,671 2/1965 Reynolds 313-350 FOREIGN PATENTS 1,143,275 2/1963 Germany.

JOHN W. HUCKERT, Primary Examiner.

A. J. JAMES, Assistant Examiner. 

1. A DOUBLE FRAME GRID FOR ELECTRIC DISCHARGE TUBES, COMPRISING, IN COMBINATION: A FIRST PAIR OF SPACED, SUBSTANTIALLY PARALLEL RODS, A SECOND PAIR OF SPACED, SUBSTANTIALLY PARALLEL RODS OF LARGER DIAMETER THAN SAID FIRST PAIR OF RODS, SAID FIRST AND SECOND PAIRS OF RODS BEING PARALLEL TO EACH OTHER WITH SAID FIRST PAIR RODS BEING DISPOSED BETWEEN SAID SECOND PAIR OF RODS, A PLURALITY OF CROSS PIECES WHICH HOLD THE RODS, SAID CROSS PIECES BEING ARRANGED IN SETS OF TWO, THE CROSS PIECES OF EACH SET BEING DISPOSED, RESPECTIVELY, ON OPPOSITE SIDES OF SAID RODS, THE DISTANCE BETWEEN THE CROSS PIECES OF EACH SET BEING DIFFERENT IN THE REGION OF SAID FIRST AND SECOND PAIR OF RODS, RESPECTIVELY A PLURALITY OF INSULATING RINGS ON EACH OF THE SECOND PAIR OF RODS, THERE BEING A RING AT EACH INTERSECTION OF A CROSS PIECE WITH ONE OF SAID SECOND PAIR OF RODS, AND FIRST AND SECOND GRIDS WOUND, RESPECTIVELY, ON SAID FIRST AND SECOND PAIRS OF RODS. 